842 PROFESSOR W. C. M'INTOSH AND MR E. E. PRINCE ON 



bring out this feature, since the temperature was thus proportionally high. Moreover,, 

 as indicated in the Report of the Royal Commission on Trawling just mentioned, with, 

 reference to Hi%)poglo$soides limandoides (Rough Dab) and other species, comparatively 

 small specimens of both sexes are capable of successful reproduction. Thus females not 

 more than 4^ inches long, and males a little larger (7-| inches), have been paired with 

 perfect success. 



Ova fertilised at 4 p.m. on 1st April 1886, showed a wrinkled condition of the zona 

 radiata after extrusion, but soon became smooth in outline, and the germinal cap or 

 blastodisc began to be formed. In some, however, no such protoplasmic cap appeared 

 for an hour or more. The two-celled stage was reached at 6 p.m., and the sixteen-celled 

 stage at 9.45 p.m. The minute granules of the periblast were very evident in a profile 

 view. In these ova the micropyle was generally found near the disc. Next morning 

 (9 a.m. April 6) the blastoderm had made great progress, and the cells were nearly of 

 equal size. At 1 p.m. it had extended almost as far as the equator. At 9 p.m. a large 

 germinal cavity had appeared. On focussing down to the animal pole (the egg floating 

 with the disc downward in the usual manner), a peculiar group of cells was visible, 

 probably at the apex of the blastodermic cap, since the ordinary cells of the 

 germ lay above them. Moreover, the two ova specially under examination presented 

 certain (Brownian?) movements of the granules of the region, as if from decay, 

 yet such could not have been the case, as subsequent progress proved. On the 

 7th, at 9 a.m., the embryo appeared in the centre of the embryonic shield, as 

 a long curved cylinder with an expanded and thickened head. It is proportionally 

 longer than in round fishes, such as Gadus morrhua, G. seglejinus, and others. The 

 cells of the blastoderm assume a honey-comb-like appearance — more distinct than in 

 many Teleosteans. On the evening of the same day (the 7th) the optic vesicles are, 

 well developed, and the tail shows a more evident enlargement in front of the tip 

 than in Gadus teglefinus. Kupffer's vesicle is present, while in many examples four 

 or five smaller vesicles exist on the ventral surface of the caudal enlargement. On 

 the 8th April, the vesicle referred to is larger, and situated just within the blunt knob 

 of the tail. It is a large clear bubble-like vesicle, bounded by slightly granular proto- 

 plasm (periblast) of variable thickness. The yellowish pigment, characteristic of this 

 species, now appears in the form of rounded corpuscles (PL XIX. fig. 5), which do not as 

 yet send out radial processes. Occasionally one or two clear vesicles occur under the head, 

 and they have the same appearance as Kupffer's structures. No other organs, except 

 muscle-plates and neurochord, are visible in the trunk. On issuing from the egg the 

 larvae (PI. XIX. fig. 5) float on the surface if lively, but if feeble they rest on the 

 bottom in still water, i.e., in the tanks, though it is probable that this latter phenomenon 

 does not occur in nature. They shoot with a wriggling motion along the surface, and 

 are recognised by the beautiful yellow grains of pigment ; they appear, in fact, like minute 

 clubs of transparent tissue with chrome-yellow spots. One evident patch of colour 

 lies above the posterior end of the yolk, and another midway between that point and 



